Silicone compounds such as TRIS and SiGMA represented by the formulae below are conventionally known as ophthalmic silicone monomers for use in ophthalmic devices:

TRIS (3-[tris (trimethylsiloxy)silyl]propyl methacrylate) has been proposed for use as a material for intraocular lenses in Patent Publication 1 and Non-patent Publication 1. However, TRIS is inferior in compatibility with hydrophilic monomers, such as HEMA (2-hydroxyethyl methacrylate), and when copolymerized with such hydrophilic monomers, will not provide transparent monomers, and cannot be used as a lens material.
It is also known that combination of TRIS with other hydrophilic monomers often result in strongly water-repellent surfaces in a hydrous state, and thus inconvenient for use as a soft contact lens material.
In an attempt of overcoming these drawbacks, SiGMA ([methyl bis(trimethylsiloxy)silyl propyl]glycerol methacrylate) has been developed and used as a compatibilizing monomer for silicone hydrogel contact lenses, as disclosed in Patent Publications 2 and 3.
SiGMA also acts as an oxygen permeability formulation for its moderate oxygen permeability. SiGMA is a monomer formed readily by addition reaction of methacrylic acid and 3-glycidoxypropyl[bis(trimethylsiloxy)]methyl silane, and exhibits good hydrophilicity due to its hydroxyl group.
However, providing the percentage by mass of siloxanyl groups in one molecule of a monomer is its silicone content, the total weight of the atoms constituting the siloxanyl groups in one molecule of SiGMA is 221 and the molecular weight of SiGMA is 422, so that the silicone content of SiGMA is 221/422×100=52.4%. This means that SiGMA has a lower silicone content compared to TRIS having a 72% silicone content, which makes it difficult for SiGMA to provide sufficient oxygen permeability.
On the other hand, Patent Publication 4 proposes a novel monomer produced through the reaction of a methacrylic halide and a straight chain polyether-modified silicone. However, for giving hydrophilicity by means of polyether, the ether structural unit needs to be repeated for an increased number of times, which tends to lower the silicone content. Thus it is hard to fulfill both surface hydrophilicity and oxygen permeability of resulting lenses at the same time.
In view of the above, in the art of ophthalmic silicone monomers for use in ophthalmic devices, development of hydrophilic silicone monomers is demanded which have novel molecular structures, are easy to produce, are applicable to inexpensive uses such as daily disposable devices, and have a high percentage of siloxanyl groups (silicone content) in one molecule of the monomer.